Allergies kill the cannabis buzz

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A cannabis plant. Credit: AFP

When spring-time shows itself in all its glory, allergy sufferers face an onslaught of allergens: pollen, grasses, ragweed... and marijuana.

Long under the radar of the scientific community, cannabis allergies appear to be on the rise, leading to increased attention from researchers. On the agenda of topics to be discussed at the 2014 Congress of French-Speaking Allergists, which takes place in Paris from April 16, cannabis allergies are also the subject of a recent study published in the French scientific journal La Revue Française d'Allergologie.

Four researchers at the University of Antwerp in Belgium, working in the Allergy, Immunology and Rheumatology Department of the School of Medicine, published an article on the topic entitled Emerging allergens: Cannabis.

The researchers focused in particular on Cannabis sativa, one of the two species colloquially known as marijuana (along with Cannabis indica). Allergists are finding that the illicit plant can cause allergic rhinitis (hay fever), conjunctivitis (pink eye), skin rashes and asthmatic symptoms when smoked, inhaled or chewed.

Researchers indicate that individuals exposed to the plant's pollen could experience the same symptoms. In most areas of the US and Europe, however, even where restrictions on growing cannabis are beginning to loosen, most of the plants are still grown indoors, limiting the risk of exposure for the general population.

Finally, the researchers explore the potential cross-reactive effects of cannabis, through which exposure to the plant can lead to allergic reactions to other plants, namely foods. The so-called "cannabis-fruits/vegetables" syndrome is said to involve a protein labelled as Can s 3. The specific allergens responsible for allergic reactions to cannabis, however, have not been identified. Cannabis allergy may nonetheless be diagnosed through a skin allergy test.